24

2018

Reusing vs. Recycling Water

If you mention the subject of early reclaim systems to a carwash operator with 20 years experience and ask what thoughts come to mind, you’ll probably get a description of a piece of equipment that doesn’t do a very good job treating water, needs a lot of maintenance, has filter bags to change and replace, and produces water that offends customers with its odor. Although most reclaim manufacturers have made great gains in making their systems more user friendly, they are still missing the goal of sufficiently cleaning the water.

In general, the reason that many reclaim systems blacken equipment, destroy pumps and damage nozzles is that they simply do not remove suspended soils to low enough levels. The “filtered” water these systems produce contains high concentrations of total suspended solids (TSS) less than 20 microns in size. As the water is continuously reused, the concentration of these unfiltered particles increases exponentially. To combat their inability to remove solids effectively, some systems use a fresh water makeup line with a solenoid valve to dilute the poorly filtered water with higher quality city water. If these systems were capable of filtering the solids sufficiently, dilution with city water wouldn’t be needed. Remember, a reclaim system is supposed to save you from using city water.

Overall, the surface area and the particle-retention capabilities of the filtering or separating mechanism establish the flow rate for a given system. Some filters feature microscopic projections that allow very fine particulate matter to penetrate deeply into the filter bed. These filters can effectively remove solids down to 5 microns or less.

Due to the tight filtration and the high solids removal capacity, these types of depth filters are larger in size than typical canister or cyclone systems. Consequently, if a reclaim unit has a filtration system of small canisters or cyclones, the only way for this system to meet the water demands of the wash is for the system to only take out the very largest particles and send the water on its way. That’s the reason why water from these types of systems is black in color and wreaks havoc on nozzles — it’s simply not filtered tightly enough.

In small canisters, it would take far too many vessels for the system to produce the 100 to 150 gallons per minute or more that many of today’s high-volume washes demand. Consequently, filtration is sacrificed. The biggest problem with this is pump warranties can be voided if the solids in the water are not filtered to within published tolerances. Also, the visible signs of poor filtration are all over the walls, which is not impressive to customers.

Comparing treated, recycled water with reused, dirty water is like comparing night and day. In most cases, treated, recycled water will satisfy the requirements of publicly owned treatment works. In more and more municipalities, water departments are monitoring businesses to evaluate various impurities sent to the sewer, and carwashes are moving to the head of the list. We, as operators, must be conscious of increased regulation which can and will impact our ability to function — and our reputations in the communities we serve.

Imagine my dismay at my washes when county officials showed up seven years ago and placed sampling devices in the carwash discharge stream. They collected composite samples and sent them to a laboratory. A few weeks later, we received a violation notice stating that our water discharge was out of compliance with our discharge permit. The county gave us 30 days to resolve our discharge issues or start facing fines!

We had entirely new, much more complex issues to suddenly resolve. We were no longer talking about just clogged nozzles and dirty equipment. We were now faced with removing or significantly reducing the chemical oxygen demand, biochemical oxygen demand, total suspended solids, and oil and grease levels in our discharge. We reviewed the chemistry we were using in our wash tunnel and made some changes, but still could not meet the discharge criteria imposed by our permit. But once we installed the appropriate water treatment and recycling system, we resolved this issue entirely. Since we upgraded, we’ve been tested three or four times per year for the past seven years, with no discharge compliance issues whatsoever.